docs(S2): fix clipping in Picker custom value AvatarGroup example

[reidbarber]

Fixes the AvatarGroup getting clipped when rendered as a custom value in the Picker.

✅ Pull Request Checklist:

• Included link to corresponding React Spectrum GitHub Issue.
• Added/updated unit tests and storybook for this change (for new code or code which already has tests).
• Filled out test instructions.
• Updated documentation (if it already exists for this component).
• Looked at the Accessibility Practices for this feature - Aria Practices

📝 Test Instructions:

Test the docs example and make sure the avatar group doesn't get clipped.

🧢 Your Project:

[rspbot]

Build successful! 🎉

• View the storybook
• View the S2 storybook
• View the S2 docs
• View the React Aria docs

[snowystinger]

I'm ok with it, though a bit unfortunate that it doesn't left align the avatar with the placeholder
Do you have a screenshot of what it looks like without this change? I'm not sure where this ask came from

[reidbarber]

@snowystinger Found in testing yesterday, the group gets barely clipped on the left.